Premature delivery is one of the abnormalities which occur accompanied with pregnancy. It is caused by various reasons but ascendens infection, intrauterine infection and abruption of placenta are considered as main reasons.
In the case where the premature delivery occurs because of an infectious disease or chorionic amnionitis, the concentration of C-reactive protein (CRP) and the leukocyte count both in the blood of the mother's body show an increase so that premature delivery is checked by measuring these values.
It is however difficult to say that the CRP concentration and the leukocyte count are specific to the premature delivery, because they are the values available from the blood and show an increase even by the factors other than the premature delivery. In addition, the CRP is accompanied with the problem that it can be detected only in a trace amount in the blood so the sensitivity of the measurement is low. Thus, it is difficult to make diagnosis as premature delivery at early stages of pregnancy by measuring the CRP concentration or the leukocyte count in the blood.
On the contrary, a method of making diagnosis as abortion or premature delivery by measuring Interleukin-6 (IL-6) in the blood has recently been reported (Japanese Patent Application No. 209882/1993). This method however uses the blood from the mother's body as a specimen and therefore is not fully satisfactory from the viewpoints of inferiority both in sensitivity and specificity.
An object of the present invention is therefore to search a substance which will be an indication of premature delivery and to establish a method for differentiating it.
With the forgoing in view, the present inventors have conducted an extensive investigation. As a result, it has been found that an increase in Interleukin-8 (IL-8) in the vaginal secretory fluid or cervical mucus is specific to a pregnant woman suffering from the threatened premature delivery and the vaginal secretory fluid or cervical mucus of the pregnant woman suffering from the threatened premature delivery can be differentiated by measuring the IL-8 amount, leading to the completion of the invention.